It was demonstrated by Geschwind and Levitsky (1968) that large left-right asymmetries exist in the cerebral cortex of adult humans, in areas which are probably involved in language functions. These results have been confirmed by Wada, Teszner, Witelson and Pallie, and Yeni-Komshian and Benson. These asymmetries appear to exist in human fetuses (Wada; Gilles; personal communication), and in non-human primates (Yeni-Komshian; Geschwind and LeMay). Pilot studies by Galaburda and Sanides have shown that the gross anatomical asymmetries probably represent differences in extent of cytoarchitectonic areas. It is proposed by cytoarchitectonic mapping to specify the precise extent of regions whose areas differ on the two sides. The studies will be carried out on whole brain material prepared with conventional Nissl stains and also on brains stained for lipofuscin by the pigmentarchitectonic method of Braak. The results will be compared with studies of asymmetries observed radiologically, in particular with EMI Scans.